Description(provided by applicant): Infections caused by gram negative bacteria may be complicated by sepsis, multi-organ failure and death. Since the mortality has not changed during the last decade, new strategies to supplement conventional antibiotic therapy and supportive care are required. We developed a vaccine composed of detoxified lipopolysaccharide (LPS) from E coli 0111:B4, Rc (J5) chemotype complexed to the outer membrane protein of group B meningococcus (J5 dLPS/ OMP vaccine). This vaccine induces antibodies to a highly conserved region of bacterial LPS that are protective both actively and passively in animal models of sepsis. In the last grant period we administered this vaccine to 24 human subjects. The vaccine was safe and well-tolerated, but the antibody response was lower than that measured in rabbits and rodents. Consequently, in this proposal we wish evaluate the safety, immunogenicity and functional activity of this vaccine when given with the adjuvants MF-59 and oligonucleotide (CpG), each of which has been safely administered to humans. Earlier, we found that vaccine-induced antibody bound heterologous LPS, enhanced the clearance of bacteria and endotoxin from the circulation of rats and neutralized the ability of LPS to induce cytokines ex vivo and to prime superoxide formation by human neutrophils. We now will correlate antibody levels following vaccine/adjuvant immunization with functional activity in vivo (clearance studies and protective activity) and in vitro (LPS binding and LPS neutralization studies). These activities may serve as surrogate markers for vaccine efficacy. (Specific Aim I). We then will do a phase I study of vaccine and adjuvants in human subjects (Specific Aim II). J5 LPS inhibits the binding of vaccine-induced antibody to heterologous LPS. We therefore will determine if there is a specific J5 LPS epitope by comparing the inhibitory activity of complete and subunit structures of J5 LPS with other core LPS species, and will develop monoclonal antibodies to this epitope with the vaccine (Specific Aim III). The role of complement, macrophages and neutrophils in the functional activity of anti-J5 dLPS antibodies will be defined as well as the effect of immunization on LPS surface receptors (toll-like receptor 4 and CD14) of cells from both animals and human subjects (Specific Aim IV). If successful, these studies will lead to Phase II and III studies for the prevention and treatment of sepsis.